Discovery 4 transmission

[Darryl C]

Hi this is my first post so hope to get it right !
We have a D4 and are towing a 2.6 T single axle caravan and would like to know if others have experienced gear changes while towing. When we left Mt Isa, outside temp was around 27degrees, the car drove normal up and down inclines without dropping down into 7th except on steeper hills where it was to be expected. As the out side temp rose 40, the gear changes were more often, even on the slight gradients. In the end I switched to sport mode and locked it into 7th. This has continued all the way to Katherine so far. Could this be caused by transmission oil getting too hot and if so is there anything I should do. The trans oil is to be changed when we get back to Townsville after this trip. We currently have 130,000 km on the clock. Fuel consumption 15-18L/100 similar to other trips.

[loanrangie]

Has the fluid been changed at all, if not its time for a service.

[Discodicky]

Hi this is my first post so hope to get it right !
We have a D4 and are towing a 2.6 T single axle caravan and would like to know if others have experienced gear changes while towing. When we left Mt Isa, outside temp was around 27degrees, the car drove normal up and down inclines without dropping down into 7th except on steeper hills where it was to be expected. As the out side temp rose 40, the gear changes were more often, even on the slight gradients. In the end I switched to sport mode and locked it into 7th. This has continued all the way to Katherine so far. Could this be caused by transmission oil getting too hot and if so is there anything I should do. The trans oil is to be changed when we get back to Townsville after this trip. We currently have 130,000 km on the clock. Fuel consumption 15-18L/100 similar to other trips.

Definitely due for an oil change at 130k if not already done!
Suggest changing oil every 60-80,000 if towing often.
I have an 8 speed trans (MY13 D4) and always use Sport mode when towing my 3.0T van, and usually change gears manually to keep engine rpm between around 2300-2700
I use a Scanguage 2 which shows auto oil temp which, for example, on a 25 deg day (hot here in Tassy ) when climbing a long hill the auto temp will rise to around 100-104 deg, sometimes slightly higher, but will soon drop back to middle 90's when going down the hill.

Yes, I think your oil was staying too hot; you may have been experiencing too much (too often) convertor slipping by not manually changing, depending on terrain.

Your fuel cons is about what I experience.

[Barraman]

I posted this in an earlier thread.

I have towed a 2.5T boat/trailer some 50,000 km over the last 5 years with my 2015 D4 TDV6 8 speed. I have towed in D and S - get slightly better economy in S but I can't say I notice any difference.
I pretty much always use the cruise control. I generally tow on the speed limit.
It mostly tows in 8 or 7 sitting on 1600 rpm at 100 kph in 8 and 1800 in 7. It changes down to 6 for a hill, occasionally 5, rarely lower except for very steep climbs. If it needs to go lower than 5, the cruise control drops out.
I have tried driving on the paddles but find it to be a pain in the bum with a vehicle that tows so easily.
Sitting on 100 kph on a flat road on a 30oC day, the coolant temp sits on 100, the transmission oil temp 95, the sump oil temp 125 and the torque around 250 (max torque about 476), so its not working hard.
It uses on average 17.5 L/100 km towing the boat.
Best towing/cruising vehicle I have ever driven.

I can’t imagine towing for any length of time at 23 - 2700 rpm!